A popular academic theory of constitutions holds that constitutions serve to commit the polity across time. Knowing that we are likely to try to impose majority will on minorities in the future, we tie our collective hands to limit the damage that can be done to individual and community rights. Knowing that we are likely to prefer to continuously re-elect incumbents, we impose term limits that force us to choose new candidates, limiting democratic choice. There are many other examples in the literature, which is associated with scholars like Cass Sunstein and Stephen Holmes.
From this point of view, it is somewhat odd that constitutions do not more frequently limit the size or growth of government in budgetary terms. It might make sense, for example, to pre-commit not to engage in deficit spending over a certain percentage. To be sure there are lots of examples of constitutional provisions that set aside a certain percentage of the revenue for particular allocations, and some examples of restrictions on extra-budgetary spending (Austria’s Art. 51b limits it to 1/1000 of total spending, unless there is a state of defense; other constitutions prohibit extra-budgetary spending entirely.) But I know of no constitution that imposes an explicit limit on the size of the state. Relatively few national constitutions require a balanced budget, even as an aspiration. Switzerland provides one example: Art. 126 makes reference to a balanced budget over the long term and states that “The maximum of the total expenditures which may be budgeted shall be determined by the expected receipts, taking into account the economic situation.” Article 128 actually spells out the maximum personal income tax rates, so presumably when one combines limited taxes and a sort-of balanced budget requirement, there are fairly rigid limits on state spending. But the whole Swiss constitution can be amended through referendum so the level of pre-commitment is not that high.
The main point is that, while constitutions sometimes involve precommitments, they do not always do so in areas we might think they should. And many provisions of constitutions don’t seem well explained by precommitment theory: why do so many spend so much time on issues like the national anthem and oaths of office that could easily be dealt with in statutes?